Input/output, Inc.

I/o Sensors, Inc.

I/o of Austin, Inc.

Ion Geophysical Corporation

Michael L Abrams

Richard A Johnson

Ben William Jones

Scott T Dupuie

Franklin W Mayo

Mark E Burchfield

Roger Maher

Burton A Devolk

Jeffery C Gannon

Paul E Carroll

Jeffrey Blackburn

Mauricio A Zavaleta

Charles Geoffrey Rice

Mauricio Zavaleta

Roy W James, Iii

Frank Mayo

James Broseghini

Ben Jones

Jeffrey A Blackburn

A system for acquiring environmental information measurements. The 5 system () utilize a sensor, () a front-end circuit, () a loop filter (), a switch controller (), and a reduced-order loop control circuit to provide reliable data measurements while providing robust system behavior. The system further includes a sensor simulator () for simulating the operation of the sensor () and testing the operation of the front-end circuit () and the loop filter ().

Sensor

A high performance method and apparatus for testing a closed loop transducer is disclosed. A test bitstream signal is combined with a .SIGMA..DELTA. feedback bitstream of the transducer to produce a combined bitstream which is converted to a physical feedback to the sensor of the transducer. The .SIGMA..DELTA. bitstream output of the transducer is recorded for later analysis so as to test characteristics of the transducer. The test bitstream signal is preferably an oversampled, pulse density modulated signal. A testing arrangement is provided which is based upon the storage of short-length test patterns which are repetitively accessed to form a continuous test pattern. The test bitstream provided by the method of the invention produces very low noise and low distortion test signals where a repetitive test pattern is equivalent in length to one period of the test signal.

Method and apparatus for generation of test bitstreams and testing of

A method and apparatus for measuring and compensating for stray capacitance of a micro-machined sensor of an accelerometer system is disclosed. Stray capacitance differences between a top plate and a sensing element and between a bottom plate and the sensing element degrade accelerometer performance if not compensated for. Measurement of stray capacitance difference is achieved by operating the accelerometer in two calibration phases and measuring the steady-state output voltage in each of the two phases. In calibration phase 1, no force is applied to the sensor during clock intervals 1-4. In calibration phase 2, a dummy force up is applied and then a dummy force down is applied during those intervals 1-4. The difference in the output voltage of the two calibration phases is representative of the difference in stray capacitance of the sensor. Capacitance is added to the top or bottom plates in an amount proportional to the measured stray capacitance. The procedure is repeated until the voltage difference of the two calibration phases is zeroed, which is indicative that the inherent stray capacitance has been zeroed.

Method and apparatus for calibration of stray capacitance mismatch in a

The system for suppressing an ambient noise signal which comtaminates a desired signal includes a noise pickup detector for detecting the ambient noise signal. A noise discriminator processes the detected noise signal into noise data. A reference noise generator converts the noise data into a reference noise signal. The noise generator automatically adjusts the reference noise signal to correspond with changes in the noise signal as it is being detected. A filter filters the reference noise signal into an error signal which is adapted to remove the noise signal from the contaminated signal. A cross-correlator cross-correlates the contaminated signal with the reference noise signal and adjusts the filter to produce the required error signal.

Noise suppression during seismic exploration

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Houston, TX, United States of America

Michael L Abrams